Vaginal and urinary microbiomes in postmenopausal women and breast cancer survivors and their associations with genitourinary syndrome of menopause: a scoping review.

Genitourinary syndrome of menopause (GSM) is common among postmenopausal women and breast cancer survivors, particularly those receiving antiestrogen therapy. However, the role of the urinary and vaginal microbiomes in GSM remains underexplored. This study aimed to evaluate urinary and vaginal microbiome differences and their association with GSM in postmenopausal women and breast cancer survivors. A scoping review (PubMed, Embase; May 2025) identified 877 studies addressing the vaginal or urinary microbiome in postmenopausal women and 242 studies in breast cancer survivors. After screening and eligibility assessment, 18 studies involving postmenopausal women and three studies involving breast cancer survivors were included. Across 21 included studies (n = 30-1320 participants), Lactobacillus depletion and anaerobic overgrowth (e.g. Gardnerella, Prevotella, Sneathia) were associated with GSM. Postmenopausal women with low-Lactobacillus community state types (CSTs) had up to 25.9-fold higher odds of GSM. In breast cancer survivors, Lactobacillus was nearly absent (5% of samples), with increased Gardnerella and Sneathia in symptomatic women. Associations between Lactobacillus relative abundance and symptom severity were inconsistent. In conclusion, GSM appears to be associated with microbial dysbiosis characterized by anaerobic overgrowth, rather than Lactobacillus depletion alone. Estrogen suppression in breast cancer survivors may exacerbate dysbiosis and symptoms, highlighting the need for microbiome-targeted treatments.